CN104833122B - Refrigerating plant - Google Patents

Abstract

The present invention provides a kind of refrigerating plant.Solve in reaching the refrigerating plant of supercritical pressure in high-pressure side, the problem of during using the refrigerant for flowing out evaporator the refrigerant of eluting gas cooler to be subcooled.The refrigerating plant possesses：Heat exchanger (29), is arranged on the downstream of gas cooler (28) and the upstream side of electric expansion valve (33)；Bypass circulation (60), is connected in parallel relative to the series loop of electric expansion valve (39) and evaporator (41)；Electric expansion valve (65), is arranged in bypass circulation；And control device (57), and, make the first flow path (29A) of refrigerant inflow heat exchanger (29) that compressor (11) is flowed out and be sucked into from evaporator, make the second flow path (29B) of refrigerant inflow heat exchanger (29) that electric expansion valve (33) is flowed out and flowed into from gas cooler, thus, the refrigerant of the flowing in the second flow path (29B) of heat exchanger (29) is subcooled by the refrigerant of the flowing in the first flow path (29A) of heat exchanger (29).

Description

freezer

technical field

The invention relates to a refrigerating device whose refrigerant circuit is composed of a compression mechanism, a gas cooler, a main throttling mechanism and an evaporator, and the high-pressure side reaches supercritical pressure.

Background technique

In the past, this type of refrigeration device constituted a refrigeration cycle by a compression mechanism, a gas cooler, and a throttling mechanism. The refrigerant evaporates, and the surrounding air is cooled by the evaporation of the refrigerant at this time. In recent years, Freon-based refrigerants have been gradually no longer used in such refrigerating devices due to natural environmental problems and the like. Therefore, the use of carbon dioxide, which is a natural refrigerant, as a substitute for Freon refrigerants is being developed. It is known that this carbon dioxide refrigerant is a refrigerant having a severe high-pressure difference and has a low critical pressure, and that compression causes the high-pressure side of the refrigerant cycle to reach a supercritical state (for example, refer to Patent Document 1).

In addition, in the heat pump device constituting the water heater, carbon dioxide refrigerant, which can obtain excellent heating effect by the gas cooler, is gradually being used. Expansion is performed in two stages, and a gas-liquid separator is provided between each expansion device, so that gas can be injected into the compressor (for example, refer to Patent Document 2).

On the other hand, for a refrigeration device installed in an evaporator such as a showcase to cool the inside of the cabinet by using heat absorption, the temperature at the outlet of the gas cooler is high due to the high temperature of the outside air (the temperature of the heat source on the side of the gas cooler). Under the condition that the temperature of the refrigerant becomes higher, the specific enthalpy at the inlet of the evaporator becomes larger, so there is a problem that the refrigerating capacity drops significantly. At this time, if the discharge pressure (high pressure side pressure) of the compression mechanism is increased in order to ensure the refrigeration capacity, the compression power will increase and the coefficient of performance will decrease.

Therefore, a so-called separation cycle refrigeration device is proposed, which divides the refrigerant cooled by the gas cooler into two refrigerant flows, and makes the split refrigerant flow through the auxiliary throttling mechanism to flow into the separation heat. One path of the exchanger returns to the intermediate pressure part of the compressor (compression mechanism), and another refrigerant flow flows into the other flow path of the separation heat exchanger for heat exchange, and then flows into the evaporator through the main throttling mechanism. According to such a refrigeration system, the second refrigerant flow can be cooled by the decompressed and expanded first refrigerant flow, and the specific enthalpy at the inlet of the evaporator can be reduced to improve the refrigeration capacity (for example, refer to Patent Document 3).

prior art literature

patent documents

Patent Document 1: Japanese Patent Publication No. 7-18602

Patent Document 2: Japanese Patent Laid-Open No. 2007-178042

Patent Document 3: Japanese Patent Laid-Open No. 2011-133207

Contents of the invention

The problem to be solved by the invention

As another method of reducing the specific enthalpy at the inlet of the evaporator as described above, it is considered to install a heat exchanger at the outlet of the gas cooler, so that the refrigerant flowing out of the high-pressure side of the gas cooler and the refrigerant flowing out of the low-pressure side of the evaporator flow in separately. The two flow paths of the heat exchanger use the refrigerant on the low-pressure side to cool the refrigerant on the high-pressure side.

This method can also subcool the refrigerant flowing into the main throttling mechanism, but there is a problem that the temperature of the refrigerant flowing out of the heat exchanger and sucked into the low-pressure side of the compressor will rise, so with the increase of the suction temperature If the temperature rises, the temperature inside the compressor will rise (the temperature of the refrigerant in the intermediate pressure part and the temperature of the discharged refrigerant will rise), and the operating efficiency of the compressor will decrease, and there will be a risk of damage.

The present invention was made to solve this conventional technical problem, and its object is to solve the problem when the refrigerant flowing out of the evaporator is used to subcool the refrigerant flowing out of the gas cooler in a refrigeration device whose high pressure side reaches supercritical pressure. .

solution to the problem

The refrigerating device of the present invention consists of a compression mechanism, a gas cooler, a main throttling mechanism, and an evaporator to form a refrigerant circuit, and the high pressure side reaches a supercritical pressure. The refrigerating device includes: a throttling mechanism for pressure adjustment, connected to the The refrigerant circuit on the downstream side of the regulator and the upstream side of the main throttling mechanism; the liquid receiver is connected to the refrigerant circuit on the downstream side of the pressure adjustment throttling mechanism and the upstream side of the main throttling mechanism; the heat exchanger is arranged on the gas cooling In the refrigerant circuit on the downstream side of the pressure regulator and the upstream side of the throttling mechanism for pressure adjustment; the main circuit reaches the liquid receiver from the gas cooler through the heat exchanger and the throttling mechanism for pressure adjustment, so that the refrigerant flows from the lower part of the liquid receiver The outflow flows into the main throttling mechanism; the auxiliary circuit makes the refrigerant in the liquid receiver return to the intermediate pressure part of the compression mechanism through the auxiliary throttling mechanism; the bypass circuit is connected in parallel with the series circuit of the main throttling mechanism and the evaporator connection; the throttling mechanism for bypass is set in the bypass circuit; and the control mechanism controls the throttling mechanism for pressure adjustment, the auxiliary throttling mechanism and the throttling mechanism for bypass, so that the gas flowing out of the evaporator and sucked into the compression mechanism The refrigerant flows into the first flow path of the heat exchanger, and the refrigerant that flows out of the gas cooler and flows into the pressure adjustment throttling mechanism flows into the second flow path of the heat exchanger, thereby passing through the first flow path of the heat exchanger. The refrigerant flowing in the second flow path of the heat exchanger is used to subcool the refrigerant flowing in the second flow path of the heat exchanger.

In the refrigerating apparatus of claim 2, in the above-mentioned claim, the control means controls the intake temperature of the refrigerant sucked into the low pressure side of the compression means to a predetermined target value through the bypass throttling means.

The refrigerating device of claim 3, in each of the above-mentioned solutions, includes an internal heat exchanger arranged in the refrigerant circuit on the downstream side of the accumulator and on the upstream side of the main throttling mechanism, so that the The refrigerant flows into the first flow path of the internal heat exchanger, so that the refrigerant flowing out from the lower part of the accumulator and flows to the main throttling mechanism flows into the second flow path of the internal heat exchanger, thereby passing through the first flow path of the internal heat exchanger The refrigerant flowing in the internal heat exchanger subcools the refrigerant flowing in the second flow path of the internal heat exchanger.

A refrigerating apparatus according to a fourth aspect, in each of the above-mentioned aspects, wherein the control means controls the high-pressure side pressure of the refrigerant circuit upstream of the pressure-adjusting throttling mechanism to a predetermined target value through the pressure-adjusting throttling mechanism.

The refrigerating device according to claim 5, in each of the above-mentioned solutions, the auxiliary throttling mechanism has a throttling mechanism for the first auxiliary circuit, and the auxiliary circuit has a throttling mechanism for letting the refrigerant flow out from the upper part of the liquid receiver and flow into the first auxiliary circuit. The control mechanism controls the pressure of the refrigerant in the accumulator to a specified target value through the throttling mechanism for the first auxiliary circuit.

The refrigerating device according to claim 6, in each of the above-mentioned means, the auxiliary throttling mechanism has a throttling mechanism for the second auxiliary circuit, and the auxiliary circuit has a throttling mechanism for letting the refrigerant flow out from the lower part of the accumulator and flow into the second auxiliary circuit The control mechanism controls the discharge temperature of the refrigerant discharged from the compression mechanism to the gas cooler to a predetermined target value through the throttling mechanism for the second auxiliary circuit.

The refrigerating device of claim 7, in each of the above-mentioned solutions, includes a blower for cooling the gas cooler, and the control mechanism controls the operation of the blower so that the temperature of the refrigerant flowing out of the gas cooler is determined relative to the temperature of the outside air. specified target value.

The refrigerating apparatus of Claim 8 uses carbon dioxide as a refrigerant|coolant in each said Claim.

The effect of the invention

According to the present invention, the refrigeration device consists of a compression mechanism, a gas cooler, a main throttling mechanism and an evaporator to form a refrigerant circuit, and the high-pressure side reaches supercritical pressure. The refrigeration device includes: a throttling mechanism for pressure adjustment, connected to the gas cooling The refrigerant circuit on the downstream side of the regulator and the upstream side of the main throttling mechanism; the liquid receiver is connected to the refrigerant circuit on the downstream side of the pressure adjustment throttling mechanism and the upstream side of the main throttling mechanism; the heat exchanger is arranged on the gas cooling In the refrigerant circuit on the downstream side of the pressure regulator and the upstream side of the throttling mechanism for pressure adjustment; the main circuit reaches the liquid receiver from the gas cooler through the heat exchanger and the throttling mechanism for pressure adjustment, so that the refrigerant flows from the lower part of the liquid receiver The outflow flows into the main throttling mechanism; the auxiliary circuit makes the refrigerant in the liquid receiver return to the intermediate pressure part of the compression mechanism through the auxiliary throttling mechanism; the bypass circuit is connected in parallel with the series circuit of the main throttling mechanism and the evaporator connection; the throttling mechanism for bypass is set in the bypass circuit; and the control mechanism controls the throttling mechanism for pressure adjustment, the auxiliary throttling mechanism and the throttling mechanism for bypass, so that the gas flowing out of the evaporator and sucked into the compression mechanism The refrigerant flows into the first flow path of the heat exchanger, and the refrigerant that flows out of the gas cooler and flows into the pressure adjustment throttling mechanism flows into the second flow path of the heat exchanger, so that it can pass through the first flow path of the heat exchanger. The low-pressure side refrigerant flowing in the medium is used to subcool the refrigerant flowing in the second flow path of the heat exchanger, and the dryness of the refrigerant at the outlet of the throttle mechanism for pressure adjustment is reduced.

The refrigerant flowing in the second flow path of the heat exchanger enters the accumulator through the throttling mechanism for pressure adjustment, flows out from the lower part of the accumulator, and flows into the evaporator after being throttled by the main throttling mechanism, so that the refrigerant can pass heat The subcooling in the exchanger reduces the specific enthalpy at the inlet of the evaporator, which can effectively improve the refrigeration capacity.

In addition, part of the refrigerant liquefied by expansion in the pressure adjusting throttle mechanism evaporates in the accumulator to become gaseous refrigerant whose temperature drops, and the rest becomes liquid refrigerant and is temporarily stored in the lower part of the accumulator. Then, the liquid refrigerant in the lower part of the accumulator will flow into the main throttling mechanism, so the refrigerant can flow into the main throttling mechanism in a liquid-filled state, especially under refrigeration conditions where the evaporation temperature in the evaporator is high. Improved freezing capacity.

Furthermore, since fluctuations in the amount of circulating refrigerant in the refrigerant circuit are absorbed by the accumulator, there is also an effect of eliminating errors in the amount of refrigerant charged.

In particular, the refrigerating apparatus of the present invention includes a bypass circuit connected in parallel to the series circuit of the main throttling mechanism and the evaporator, and a throttling mechanism for bypass provided in the bypass circuit. The bypass throttling mechanism allows the refrigerant to bypass the main throttling mechanism and the evaporator and flow into the first flow path of the heat exchanger, and the suction temperature of the refrigerant evaporated therein and sucked into the low-pressure side of the compression mechanism is controlled to a specified value. By setting the target value, an increase in the suction temperature of the refrigerant in the compression mechanism can be prevented, and a decrease in the operating efficiency of the compression mechanism or occurrence of damage can be avoided before it happens.

Furthermore, as in Solution 3, if an internal heat exchanger is installed in the refrigerant circuit on the downstream side of the accumulator and upstream of the main throttling mechanism, the refrigerant that flows out of the evaporator and flows into the heat exchanger flows into the internal heat exchanger. The first flow path of the exchanger makes the refrigerant flowing out from the lower part of the accumulator and flows to the main throttling mechanism flow into the second flow path of the internal heat exchanger, so that the low-pressure flow flowing in the first flow path of the internal heat exchanger can pass The side refrigerant is used to supercool the refrigerant flowing out of the liquid receiver and flowing in the second flow path of the internal heat exchanger, thereby suppressing the re-expansion of the liquid refrigerant flowing out of the liquid receiver and realizing refrigeration ability to further improve.

In addition, according to means 4, in addition to the above-mentioned means, the control mechanism controls the high-pressure side pressure of the refrigerant circuit upstream of the pressure adjusting throttling mechanism to a predetermined target value through the pressure adjusting throttling mechanism, so that the The pressure of the high-pressure side where the refrigerant is discharged from the compression mechanism increases, thereby reducing the operating efficiency of the compression mechanism or causing damage to the compression mechanism.

In addition, according to means 5, in addition to the above-mentioned means, the auxiliary throttling mechanism has the throttling mechanism for the first auxiliary circuit, and the auxiliary circuit has a mechanism for causing the refrigerant to flow out from the upper part of the accumulator and flow into the throttling mechanism for the first auxiliary circuit. In the gas pipeline, the control mechanism controls the pressure of the refrigerant in the accumulator to a predetermined target value through the throttling mechanism for the first auxiliary circuit, so that the pressure fluctuation on the high pressure side can be suppressed by the throttling mechanism for the first auxiliary circuit. Therefore, it is possible to control the pressure of the refrigerant conveyed from the lower part of the accumulator to the main throttling mechanism.

In addition, the first auxiliary circuit uses the throttling mechanism to reduce the pressure of the refrigerant flowing into the main throttling mechanism, so that piping with a high pressure resistance can be used as the piping leading to the main throttling mechanism. Thereby, improvement of workability and construction cost can be aimed at.

In particular, the pressure in the accumulator is lowered by extracting low-temperature gas from the upper portion of the accumulator through the throttle mechanism for the first auxiliary circuit. As a result, the temperature in the accumulator drops, so that condensation of the refrigerant occurs, and the refrigerant in a liquid state can be efficiently stored in the accumulator.

In addition, according to means 6, in addition to the above-mentioned means, the auxiliary throttling mechanism has the throttling mechanism for the second auxiliary circuit, and the auxiliary circuit has a mechanism for causing the refrigerant to flow out from the lower part of the accumulator and flow into the throttling mechanism for the second auxiliary circuit. In the liquid pipeline, the control mechanism controls the discharge temperature of the refrigerant discharged from the compression mechanism to the gas cooler to a specified target value through the throttling mechanism for the second auxiliary circuit, so the so-called to cool the compression mechanism, thereby avoiding the problem that the temperature of the refrigerant injection from the compression mechanism becomes too high.

Furthermore, according to the seventh solution, in addition to the above-mentioned solutions, a blower for air cooling the gas cooler is included, and the control mechanism controls the operation of the blower so that the temperature of the refrigerant flowing out of the gas cooler is determined relative to the temperature of the outside air. Therefore, it is possible to keep the temperature of the refrigerant at the outlet of the gas cooler at an appropriate value while suppressing unnecessary operation of the blower for air cooling the gas cooler. On the other hand, the pressure on the high pressure side can be controlled by the pressure adjustment throttling mechanism as in the solution 4. Through these measures, the protection of the compression mechanism can be realized and stable operation can be maintained.

In particular, when carbon dioxide is used as the refrigerant as in the eighth aspect, the refrigeration capacity can be effectively improved by the above-mentioned aspects, and performance can be improved.

Description of drawings

Fig. 1 is a refrigerant circuit diagram of a refrigeration system according to an embodiment of the present invention (Embodiment 1).

Fig. 2 is a P-h diagram of a refrigerant circuit of the refrigeration system shown in Fig. 1 .

Fig. 3 is a refrigerant circuit diagram of a refrigeration system according to another embodiment of the present invention (Embodiment 2).

Fig. 4 is a P-h diagram of the refrigerant circuit of the refrigeration system shown in Fig. 3 .

Label description

R freezer

1 Refrigerant circuit

3 freezer unit

4 showcases

8.9 Refrigerant piping

11 compressor

22 Refrigerant introduction piping

26 Intermediate pressure suction piping

28 gas cooler

29 heat exchanger

29A First Stream

29B Second flow path

32 Gas cooler outlet piping

33 Electric expansion valve (throttle mechanism for pressure adjustment)

36 Reservoir

37 Gas cooler outlet piping

38 main circuit

39 Electric expansion valve (main throttling mechanism)

41 evaporator

42 gas pipeline

43 Electric expansion valve (throttling mechanism for the first auxiliary circuit)

44 Return piping

46 liquid pipeline

47 Electric expansion valve (throttling mechanism for the second auxiliary circuit)

48 auxiliary circuit

57 Control device (control mechanism)

60 Bypass circuit

65 Electric expansion valve (throttling mechanism for bypass)

68 Internal heat exchanger

68A First stream

68B Second flow path

Detailed ways

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Example 1]

(1) Structure of refrigeration unit R

Fig. 1 is a refrigerant circuit diagram of a refrigeration device R according to an embodiment of the present invention. The refrigerating apparatus R in this embodiment includes a refrigerating machine unit 3 installed in an equipment room of a store such as a supermarket, and one or more (only one is shown in the drawing) display cabinets 4 installed in a sales floor of the store. These refrigerator units 3 and showcases 4 are connected by refrigerant pipes (liquid pipes) 8 and refrigerant pipes 9 via unit outlets 6 and unit inlets 7 to form a predetermined refrigerant circuit 1 .

The refrigerant circuit 1 of the embodiment uses carbon dioxide (R744) whose refrigerant pressure on the high-pressure side is equal to or higher than its critical pressure (supercritical) as a refrigerant. This carbon dioxide refrigerant is a natural refrigerant that is friendly to the global environment and considers flammability, toxicity, and the like. In addition, conventional oils such as mineral oil, alkylbenzene oil, ether oil, ester oil, and PAG (polyalkylene glycol) are used as the lubricating oil.

The refrigerator unit 3 includes a compressor 11 as a compression mechanism. In this embodiment, the compressor 11 is an internal intermediate pressure type two-stage compression rotary compressor, including a closed container 12 and a rotary compression mechanism part, and the rotary compression mechanism part includes an electric element (driver) arranged and accommodated in the closed container 12. element) 13 , a first (low-stage side) rotary compression element (first compression element) 14 and a second (high-stage side) rotary compression element (second compression element) 16 driven by the rotation shaft of the electric element 13 .

The first rotary compression element 14 of the compressor 11 compresses the low-pressure refrigerant sucked into the compressor 11 from the low-pressure side of the refrigerant circuit 1 through the refrigerant pipe 9 , raises the pressure to an intermediate pressure, and discharges it to the airtight container 12 Inside, the second rotary compression element 16 further sucks in the intermediate-pressure refrigerant compressed by the first rotary compression element 14 , compresses it to increase its pressure to a high pressure, and discharges it toward the high-pressure side of the refrigerant circuit 1 . The compressor 11 is a variable frequency compressor, and by changing the operating frequency of the electric element 13 , the rotational speeds of the first rotary compression element 14 and the second rotary compression element 16 can be controlled.

On the side of the airtight container 12 of the compressor 11, a low-stage suction port 17 communicating with the first rotary compression element 14, a low-stage discharge port 18 communicating with the inside of the airtight container 12, and a port communicating with the second rotary compression element 16 are formed. High-stage suction port 19 and high-stage discharge port 21 . One end of the refrigerant introduction pipe 22 is connected to the low-stage side suction port 17 of the compressor 11 , and the other end is connected to the refrigerant pipe 9 at the unit inlet 7 . The low-stage suction port 17 connected to the refrigerant introduction pipe 22 communicates with the suction side of the first rotary compression element 14 , which is a low-pressure portion of the compressor 11 .

Low-pressure (LP: about 2.6 MPa in normal operation) refrigerant gas sucked into the suction side of the first rotary compression element 14 (the low-pressure part of the compressor 11 ) through the low-stage suction port 17 is compressed by the first rotary compressor. The element 14 is boosted to an intermediate pressure (MP: about 5.5 MPa in a normal operating state) and then discharged into the airtight container 12 . As a result, the inside of the airtight container 12 becomes an intermediate pressure (MP), which becomes an intermediate pressure portion of the compressor 11 .

One end of the intermediate pressure discharge pipe 23 is connected to the low-stage discharge port 18 of the compressor 11 which discharges the intermediate pressure refrigerant gas in the airtight container 12 , and the other end is connected to the inlet of the intercooler 24 . The intercooler 24 air-cools the intermediate-pressure refrigerant discharged from the first rotary compression element 14 , one end of the intermediate-pressure suction pipe 26 is connected to the outlet of the intercooler 24 , and the other end of the intermediate-pressure suction pipe 26 is connected to the outlet of the intercooler 24 . One end is connected to the high-stage side suction port 19 of the compressor 11 .

The intermediate pressure (MP) refrigerant gas sucked from the high-stage side suction port 19 to the second rotary compression element 16 is compressed in the second stage by the second rotary compression element 16 to become high temperature and high pressure (HP: in normal operation state, 9MPa supercritical pressure) refrigerant gas.

One end of the high-pressure discharge pipe 27 is connected to the high-stage side discharge port 21 communicating with the high-pressure chamber side of the second rotary compression element 16 of the compressor 11 , and the other end is connected to an inlet of a gas cooler (radiator) 28 . Reference numeral 20 denotes an oil separator interposed in the high-pressure discharge pipe 27 . The oil separator 20 separates oil from the refrigerant discharged from the compressor 11 and returns it to the airtight container 12 of the compressor 11 via the oil passage 25A and the electric valve 25B. In addition, 55 is a check valve interposed in the high-pressure discharge pipe 27 in front of the oil separator 20, and the direction of the oil separator 20 is forward.

The gas cooler 28 cools the high-pressure discharge refrigerant discharged from the compressor 11 , and a gas cooler blower 31 for cooling the gas cooler 28 is provided near the gas cooler 28 . In this embodiment, the gas cooler 28 is arranged side by side with the above-mentioned intercooler 24, and they are arranged in the same air passage.

One end of the gas cooler outlet pipe 32 is connected to the outlet of the gas cooler 28 , and the other end of the gas cooler outlet pipe 32 is connected to the inlet of an electric expansion valve 33 as a throttle mechanism for pressure adjustment. The electric expansion valve 33 is used to throttle the refrigerant flowing out of the gas cooler 28 to expand it, and to adjust the high-pressure side pressure of the refrigerant circuit 1 from the electric expansion valve 33 to the upstream side, and its outlet is via The reservoir inlet pipe 34 is connected to an upper portion of the reservoir 36 .

The accumulator 36 is a volume body (casing body) having a space with a predetermined volume inside, and one end of the accumulator outlet pipe 37 is connected to the lower part thereof, and the other end of the accumulator outlet pipe 37 is connected between the unit outlet 6 and the refrigeration unit. Agent pipe 8 is connected. In addition, the second flow path 29B of the heat exchanger 29 is interposed between the gas cooler outlet piping 32 , the gas cooler outlet piping 32 , the second flow path 29B of the heat exchanger 29 , the electric expansion valve 33 , and the storage liquid. The tank inlet pipe 34, the reservoir 36, and the reservoir outlet pipe 37 constitute the main circuit 38 in the present invention.

On the other hand, the showcase 4 installed in the store is connected to the refrigerant pipes 8 and 9 . In the showcase 4, an electric expansion valve 39 and an evaporator 41 as a main throttling mechanism are arranged, and are connected in sequence between the refrigerant piping 8 and the refrigerant piping 9 to form a series circuit (the electric expansion valve 39 is located in the refrigerant piping 8 side, the evaporator 41 is on the side of the refrigerant pipe 9). In addition, a cooling air circulation blower (not shown) that blows air to the evaporator 41 is provided adjacent to the evaporator 41 .

Further, the refrigerant pipe 9 is connected to the low-stage side suction port 17 communicating with the first rotary compression element 14 of the compressor 11 via the refrigerant introduction pipe 22 as described above. The first flow path 29A of the heat exchanger 29 is interposed in the refrigerant introduction pipe 22 . Further, a bypass circuit 60 is connected from the accumulator outlet pipe 37 to the refrigerant introduction pipe 22 on the upstream side of the first flow path 29A of the heat exchanger 29 . This bypass circuit 60 is connected in parallel to the series circuit of the electric expansion valve 39 and the evaporator 41 , and an electric expansion valve 65 as a throttling mechanism for bypass is provided in the bypass circuit 60 .

On the other hand, one end of the gas pipe 42 is connected to the upper portion of the accumulator 36 , and the other end of the gas pipe 42 is connected to the inlet of the electric expansion valve 43 as the throttle mechanism for the first auxiliary circuit. The gas pipe 42 allows gaseous refrigerant to flow out from the upper part of the liquid receiver 36 and flow into the electric expansion valve 43 . One end of the return pipe 44 is connected to the outlet of the electric expansion valve 43 .

In addition, one end of a liquid pipe 46 communicating with the lower part of the accumulator 36 via the accumulator outlet pipe 37 is connected to the accumulator outlet pipe 37 , and the other end of the liquid pipe 46 is connected to the downstream side of the electric expansion valve 43 . The return pipe 44 communicates. In addition, an electric expansion valve 47 serving as a throttle mechanism for the second auxiliary circuit is interposed in the liquid pipe 46 . The electric expansion valve 43 (throttle mechanism for the first auxiliary circuit) and the electric expansion valve 47 (throttle mechanism for the second auxiliary circuit) constitute an auxiliary throttle mechanism in the present application. In addition, the liquid pipe 46 allows liquid refrigerant to flow out from the lower part of the accumulator 36 and flow into the electric expansion valve 47 .

Furthermore, the other end of the return pipe 44 communicates with the middle of the intermediate pressure suction pipe 26 as an example of an intermediate pressure region connected to the intermediate pressure portion of the compressor 11 . Furthermore, these return piping 44, the electric expansion valve 43, the electric expansion valve 47, the gas pipe 42, and the liquid pipe 46 constitute the auxiliary circuit 48 in the present invention. Also, 70 is a communication pipe connecting the intermediate pressure suction pipe 26 and the refrigerant introduction pipe 22 , and 75 is a solenoid valve for opening when the compressor starts to reduce the start-up load.

According to such a configuration, the electric expansion valve 33 is located on the downstream side of the gas cooler 28 and on the upstream side of the electric expansion valve 39 . In addition, the accumulator 36 is located on the downstream side of the electric expansion valve 33 and on the upstream side of the electric expansion valve 39 . Furthermore, the heat exchanger 29 is located downstream of the gas cooler 28 and upstream of the electric expansion valve 33, and constitutes the refrigerant circuit 1 of the refrigerating apparatus R in this embodiment as described above.

Various sensors are installed throughout the refrigerant circuit 1 . That is, a high-pressure sensor 49 is installed in the gas cooler outlet pipe 32 on the downstream side of the second flow path 29B of the heat exchanger 29 and on the upstream side of the electric expansion valve 33 to detect the high-pressure side pressure HP (compression pressure) of the refrigerant circuit 1 . The pressure between the high-stage side discharge port 21 of the engine 11 and the inlet of the electric expansion valve 33). In addition, a low-pressure sensor 51 is installed on the communication pipe 70 (on the side of the refrigerant introduction pipe 22 of the solenoid valve 75 ) communicating with the refrigerant introduction pipe 22 to detect the pressure LP on the low-pressure side of the refrigerant circuit 1 (outlet of the electric expansion valve 39 ). and the pressure between the low side suction port 17). In addition, an intermediate pressure sensor 52 is attached to the communication pipe 70 (on the side of the intermediate pressure suction pipe 26 of the solenoid valve 75 ) communicating with the intermediate pressure suction pipe 26 to detect the intermediate pressure MP which is the pressure in the intermediate pressure region of the refrigerant circuit 1 . (Pressures in the airtight container 12, the intercooler 24, the intermediate pressure suction pipe 26, and the high-stage side suction port 19).

In addition, a reservoir internal pressure sensor 53 for detecting the pressure TP in the reservoir 36 is attached to the gas pipe 42 . The pressure in the accumulator 36 is the pressure of the refrigerant flowing out of the refrigerator unit 3 and flowing into the electric expansion valve 39 via the refrigerant pipe 8 . In addition, in the gas cooler outlet pipe 32 on the downstream side of the gas cooler 28 and on the upstream side of the second flow path 29B of the heat exchanger 29, a gas cooler outlet temperature sensor 54 is installed to detect the temperature of the gas cooler 28 flowing into the gas cooler 28. The temperature IT of the refrigerant in the second flow path 29B of the heat exchanger 29 .

In addition, in the gas cooler outlet pipe 32 on the downstream side of the second flow path 29B of the heat exchanger 29 and on the upstream side of the electric expansion valve 33, an electric expansion valve inlet temperature sensor 56 is installed to detect the second flow out of the heat exchanger 29. The temperature OT of the refrigerant in the second flow path 29B. In addition, on the air inlet side of the gas cooler 28, an outside air temperature sensor 61 is installed to detect the outside air temperature AT. Further, a refrigerator inlet temperature sensor 62 is installed in the refrigerant introduction pipe 22 on the downstream side of the first flow path 29A of the heat exchanger 29 and in the vicinity of the lower-stage side suction port 17 to detect the first refrigerant sucked into the compressor 11 . The suction temperature ST of the refrigerant on the low-pressure side in the rotary compression element 14 . In addition, a discharge temperature sensor 67 is attached to the high-pressure discharge pipe 27 to detect the discharge temperature DT of the refrigerant discharged from the compressor 11 to the gas cooler 28 .

In addition, 63 is an intermediate pressure suction temperature sensor installed in the intermediate pressure suction pipe 26 , and detects the temperature of the intermediate pressure refrigerant sucked into the high-stage side suction port 19 . In addition, 64 is an accumulator outlet temperature sensor connected to the accumulator outlet pipe 37 , and detects the temperature of the liquid refrigerant flowing out from the lower part of the accumulator 36 . Further, 66 is a refrigerator outlet temperature sensor installed in the accumulator outlet pipe 37 in front of the unit outlet 6 , and detects the temperature of the refrigerant flowing out from the refrigerator unit 3 to the refrigerant pipe 8 .

Furthermore, these sensors 49 , 51 , 52 , 53 , 54 , 56 , 61 , 62 , 63 , 64 , 66 , and 67 are connected to input terminals of a control device 57 that constitutes a control mechanism of the refrigerator unit 3 including a microcomputer. In addition, the electric device 13 of the compressor 11, the air blower 31, the electric expansion valve (throttling mechanism for pressure adjustment) 33, the electric expansion valve (throttling mechanism for the first auxiliary circuit) 43, and the output end of the control device 57 are connected. , electric expansion valve (throttling mechanism for the second auxiliary circuit) 47, electric expansion valve 65 (throttle mechanism for bypass), electric valve 25B, electric expansion valve (main throttling mechanism) 39, the control device 57 is based on each sensor Output and set data, etc. to control these components.

In addition, in the following description, it is assumed that the electric expansion valve (main throttling mechanism) 39 on the side of the showcase 4 and the aforementioned cold air circulation blower are also controlled by the control device 57, but they are actually controlled by the main control unit of the store. device (not shown) and is controlled by a control device (not shown) on the showcase 4 side that cooperates with the control device 57. Therefore, the control mechanism in the present invention is a concept including the control device 57 and the control device on the showcase 4 side, the aforementioned main control device, and the like.

(2) Operation of refrigeration unit R

Based on the above configuration, the operation of the refrigeration device R will be described next. When the electric element 13 of the compressor 11 is driven by the control device 57 , the first rotary compression element 14 and the second rotary compression element 16 rotate, from the low-stage side suction port 17 to the suction side (low pressure part) of the first rotary compression element 14 Low-pressure (the aforementioned LP: about 2.6 MPa in a normal operating state) refrigerant gas is sucked in. Then, it is boosted to an intermediate pressure (the aforementioned MP: about 5.5 MPa in a normal operating state) by the first rotary compression element 14 and discharged into the airtight container 12 . As a result, the inside of the airtight container 12 becomes an intermediate pressure (MP) (intermediate pressure portion).

Then, the intermediate-pressure refrigerant gas in the airtight container 12 enters the intercooler 24 from the low-stage side discharge port 18 through the intermediate-pressure discharge pipe 23, where it is air-cooled, and returns to the high-stage side suction through the intermediate-pressure suction pipe 26. Mouth 19. The intermediate pressure (MP) refrigerant gas returned to the high-stage side suction port 19 is sucked into the second rotary compression element 16, and is compressed in the second stage by the second rotary compression element 16 to become high temperature and high pressure (HP: the above-mentioned normal operation The state is a refrigerant gas with a supercritical pressure of about 9 MPa), and is discharged from the high-stage side discharge port 21 to the high-pressure discharge pipe 27 .

(2-1) Control of the electric expansion valve 33

The refrigerant gas discharged to the high-pressure discharge pipe 27 flows into the gas cooler 28 through the check valve 55 and the oil separator 20 , where it is air-cooled and then flows out from the gas cooler outlet pipe 32 . The refrigerant gas entering the gas cooler outlet pipe 32 is subcooled in the second flow path 29B of the heat exchanger 29 as will be described later, and then reaches the electric expansion valve (throttle mechanism for pressure adjustment) 33 . The electric expansion valve 33 is provided to control the high-pressure side pressure HP of the refrigerant circuit 1 on the upstream side of the electric expansion valve 33 to a predetermined target value THP (for example, the aforementioned 9 MPa). Based on the output of the high-pressure sensor 49, the The control device 57 controls (PID control) the opening so that the high-pressure side pressure HP becomes the above-mentioned target value THP.

This target value THP is determined based on the temperature of the refrigerant flowing into the electric expansion valve 33 detected by the electric expansion valve inlet temperature sensor 56 . The target value THP is an appropriate value of the high-pressure side pressure HP according to the temperature of the refrigerant flowing into the electric expansion valve 33 , and the higher the temperature of the refrigerant, the higher the target value THP. In this way, by controlling the high-pressure side pressure HP on the upstream side to the target value THP by means of the electric expansion valve 33 , the high-pressure side pressure HP of the refrigerant discharged from the compressor 11 can be increased and the operating efficiency of the compressor 11 can be reduced. , or prevent the problem of damage to the compressor 11 before it happens.

The refrigerant gas in a supercritical state flowing out of the gas cooler 28 is cooled (supercooled) by the refrigerant flowing through the first flow path 29A in the second flow path 29B of the heat exchanger 29 as will be described later. The electric expansion valve 33 throttles and expands to be liquefied, and flows into the accumulator 36 from above through the accumulator inlet pipe 34 to partially evaporate. The accumulator 36 serves to temporarily store and separate liquid/gas refrigerant flowing out of the electric expansion valve 33 , and to absorb pressure fluctuations and refrigerant circulation fluctuations caused by the operation of the electric expansion valve 39 .

The liquid refrigerant stored in the lower part of the accumulator 36 flows out from the accumulator outlet pipe 37 (main circuit 38), flows out from the refrigerating unit 3, and flows into the electric expansion valve through the refrigerant pipe 8 (main throttling mechanism). 39. The refrigerant flowing into the electric expansion valve 39 is throttled and expanded there, thereby further increasing the liquid component, and flows into the evaporator 41 to be evaporated. The cooling effect is exerted by the heat absorption effect brought about by it. The control device 57 controls the opening degree of the electric expansion valve 39 so as to adjust the degree of superheat of the refrigerant in the evaporator 41 to an appropriate value based on the output of a temperature sensor (not shown) that detects the temperature on the inlet side and the outlet side of the evaporator 41 . .

The low-temperature gaseous refrigerant flowing out of the evaporator 41 returns to the refrigerator unit 3 through the refrigerant pipe 9 , and flows into the first flow path 29A of the heat exchanger 29 in the refrigerant introduction pipe 22 . After cooling (subcooling) the high-pressure side refrigerant flowing through the second flow path 29B here, it is further sucked into the low-stage side suction port communicating with the first rotary compression element 14 of the compressor 11 through the refrigerant introduction pipe 22 . Mouth 17. The above is the flow of the main circuit 38 .

(2-2) Control of the electric expansion valve 43

Next, the flow of the auxiliary circuit 48 will be described. As mentioned above, the electric expansion valve 43 (throttling mechanism for the first auxiliary circuit) is connected to the gas pipeline 42 connected to the upper part of the accumulator 36, and the gaseous refrigerant is expanded from the upper part of the liquid accumulator 36 through the electric expansion valve. The flow out of the valve 43 returns to the intermediate pressure portion of the compressor 11 through the return pipe 44 as described above.

The temperature of the gaseous refrigerant stored in the upper part of the accumulator 36 decreases due to evaporation in the accumulator 36 . In addition, the electric expansion valve 43 performs the function of throttling the refrigerant flowing out from the upper part of the accumulator 36 , and adjusts the pressure in the accumulator 36 (the pressure of the refrigerant flowing into the electric expansion valve 39 ) to The effect of the specified target value SP. Furthermore, the control device 57 controls the opening degree of the electric expansion valve 43 based on the output of the accumulator internal pressure sensor 53 . This is because, when the opening degree of the electric expansion valve 43 increases, the outflow amount of the gaseous refrigerant from the accumulator 36 increases, and the pressure in the accumulator 36 decreases.

In the embodiment, the target value SP is set to, for example, 6 MPa, which is lower than the high-pressure side pressure HP and higher than the intermediate pressure MP. Furthermore, the control device 57 calculates, for example, the pressure of the electric expansion valve 39 based on the difference between the pressure TIP in the accumulator 36 (the pressure of the refrigerant flowing into the electric expansion valve 39 ) detected by the accumulator internal pressure sensor 53 and the target value SP. The adjustment value (number of steps) of the opening degree is added to the opening degree at startup to control the pressure TIP in the accumulator 36 (the pressure of the refrigerant flowing into the electric expansion valve 39 ) to the target value SP. That is, when the pressure TIP in the accumulator 36 rises higher than the target value SP, the opening degree of the electric expansion valve 43 is increased so that the gaseous refrigerant flows out from the accumulator 36 to the gas pipe 42; When falling below the target value SP, the opening degree is reduced to control toward closing.

By controlling the pressure TIP of the refrigerant in the accumulator 36 to the target value SP by means of the electric expansion valve 43 , it is possible to suppress the influence of fluctuations in the high-pressure side pressure HP and control the flow of refrigerant from the lower part of the accumulator 36 to the electric expansion valve. 39 refrigerant pressure. In addition, by reducing the pressure of the refrigerant flowing into the electric expansion valve 39 via the electric expansion valve 43 , it is possible to use a pipe with low pressure resistance strength as the refrigerant pipe 8 . Moreover, by extracting low-temperature gas from the upper part of the accumulator 36 through the electric expansion valve 43, the pressure in the accumulator 36 drops, and the temperature drops, so that condensation of the refrigerant can occur, thereby effectively cooling the accumulator 36. Refrigerant stored in a liquid state.

(2-3) Control of electric expansion valve 47

In addition, as described above, the electric expansion valve 47 (throttling mechanism for the second auxiliary circuit) is connected to the liquid pipe 46 connected to the accumulator outlet pipe 37 at the lower part of the accumulator 36, and through this electric expansion valve 47 Part of the liquid refrigerant flowing out from the lower part of the accumulator 36 joins the gas refrigerant from the gas pipe 42 in the return pipe 44 and returns to the intermediate pressure part of the compressor 11 through the return pipe 44 as described above.

That is, the liquid refrigerant stored in the lower part of the accumulator 36 flows into the liquid pipe 46 that is separated from the accumulator outlet pipe 37 connected to the lower part and constitutes the auxiliary circuit 48, and after being throttled by the electric expansion valve 47, flows into the compressor. The second rotary compression element 16 of 11 is vaporized (injected) therein. The heat absorption at this time cools the second rotary compression element 16 of the compressor 11 .

In this way, the electric expansion valve 47 throttles the liquid refrigerant flowing out from the lower part of the accumulator 36 so that it returns to the compressor 11 and evaporates to cool the compressor 11, and the control device 57 controls the opening of the electric expansion valve 47 degree, thereby adjusting the amount of injected refrigerant toward the compressor 11.

When the amount of injected refrigerant to the compressor 11 increases, the temperature of the compressor 11 decreases, and the discharge temperature of the refrigerant discharged from the compressor 11 to the gas cooler 28 also decreases. At this time, the control device 57 controls the opening degree of the electric expansion valve 47 based on the discharge temperature DT of the refrigerant detected by the discharge temperature sensor 67 so that the discharge temperature DT becomes a predetermined target value, thereby adjusting the direction. The amount of refrigerant injected into the compressor 11. This prevents the temperature of the discharged refrigerant discharged from the second rotary compression element 16 of the compressor 11 from reaching an abnormally high temperature.

(2-4) Control of electric expansion valve 65

Next, the control of the electric expansion valve 65 by the control device 57 will be described with reference to the P-h diagram of FIG. 2 . As described above, the bypass circuit 60 is connected from the accumulator outlet pipe 37 to the refrigerant introduction pipe 22 on the upstream side of the first flow path 29A of the heat exchanger 29 , and is connected to the series circuit of the electric expansion valve 39 and the evaporator 41 . And become parallel.

Therefore, when the electric expansion valve 65 is opened, part of the liquid refrigerant flowing out from the lower part of the accumulator 36 to the accumulator outlet pipe 37 bypasses (bypasses) the electric expansion valve 39 and the evaporator 41 and flows into the bypass circuit 60 , after being throttled by the electric expansion valve 65 , the refrigerant flows into the first flow path 29A of the direct heat exchanger 29 through the refrigerant introduction pipe 22 . The refrigerant flowing into the first flow path 29A evaporates therein, so that the temperature drops. As a result, the suction temperature ST of the refrigerant sucked into the compressor 11 decreases.

Here, the refrigerant on the high-pressure side is subcooled by the refrigerant on the low-pressure side flowing out of the evaporator 41 , thereby increasing the suction temperature of the refrigerant sucked into the compressor 11 . If this temperature rise is too large, the temperature of the refrigerant sucked into the first rotary compression element 14 of the compressor 11 will increase, which will cause the intermediate-pressure refrigerant discharged from the first rotary compression element 14 The temperature is also abnormally high.

Therefore, the control device 57 controls the opening degree of the electric expansion valve 65 based on the suction temperature ST of the refrigerant flowing into the compressor 11 detected by the refrigerator inlet temperature sensor 62 so as to control the suction temperature ST to a predetermined target value (for example, +18°C, etc.). This control prevents the discharge temperature of the refrigerant from the first rotary compression element 14 of the compressor 11 from reaching a high temperature abnormally, and protects the compressor 11 .

The portion indicated by X1 in the P-h diagram of FIG. 2 is the effect brought by the electric expansion valve 65, which lowers the discharge temperature of the refrigerant from the first rotary compression element 14 from the state indicated by the dotted line to that indicated by the solid line. status. In addition, X2 in FIG. 2 is the subcooling effect in the heat exchanger 29, and the refrigerant flowing into the electric expansion valve 33 is subcooled from the state shown by the solid line to the state shown by the dotted line.

(2-5) Control of the gas cooler blower 31

Next, control of the gas cooler blower 31 by the control device 57 will be described. The control device 57 of the embodiment controls the rotation speed of the blower 31 for the gas cooler based on the temperature of the refrigerant detected by the gas cooler outlet temperature sensor 54 (the temperature of the refrigerant flowing out of the gas cooler 28) so that the temperature of the refrigerant become the specified target value. At this time, the control device 57 sets a target value for the temperature of the refrigerant flowing out of the gas cooler 28 based on the outside air temperature AT detected by the outside air temperature sensor 61 . This target value is an appropriate value for the temperature of the refrigerant (refrigerant flowing out of the gas cooler 28 ) predetermined for each outside air temperature.

In this way, the control device 57 controls the operation (rotational speed) of the blower 31 for the gas cooler so that the temperature of the refrigerant flowing out of the gas cooler 28 becomes a predetermined target value determined with respect to the outside air temperature AT, thereby suppressing the impact on the gas. The cooler 28 can maintain the temperature of the refrigerant at the outlet of the gas cooler 28 at an appropriate value by performing redundant operation of the blower 31 for the gas cooler for air cooling.

On the other hand, the control device 57 controls the high-pressure side pressure HP to a target value by using the electric expansion valve 33 on the upstream side of the accumulator 36 as described above. The cooler uses the air blower 31 to control the temperature of the refrigerant (the temperature of the refrigerant flowing out of the gas cooler 28 ) to protect the compressor 11 and maintain stable operation.

As described in detail above, in the present invention, the refrigeration device R consists of the compressor 11, the gas cooler 28, the electric expansion valve 39 and the evaporator 41 to form the refrigerant circuit 1, and the high pressure side reaches the supercritical pressure. R includes: an electric expansion valve 33 connected to the refrigerant circuit 1 on the downstream side of the gas cooler 28 and on the upstream side of the electric expansion valve 39; a liquid receiver 36 connected on the downstream side of the electric expansion valve 33 and on the upstream side of the electric expansion valve 39 The refrigerant circuit 1; the heat exchanger 29, the refrigerant circuit 1 arranged on the downstream side of the gas cooler 28 and the upstream side of the electric expansion valve 33; the main circuit 38, from the gas cooler 28 through the heat exchanger 29 and the electric expansion valve 33 reaches the accumulator 36, so that the refrigerant flows out from the lower part of the accumulator 36 and flows into the electric expansion valve 39; the auxiliary circuit 48 makes the refrigerant in the liquid accumulator 36 return to compression through the electric expansion valve 43 or the electric expansion valve 47 The intermediate pressure part of the machine 11; the bypass circuit 60 is connected in parallel with the series circuit of the electric expansion valve 39 and the evaporator 41; the electric expansion valve 65 is arranged in the bypass circuit 60; and the control device 57 controls the electric The expansion valve 33 , the electric expansion valves 43 , 47 and the electric expansion valve 65 allow the refrigerant flowing out of the evaporator 41 and sucked into the compressor 11 to flow into the first flow path 29A of the heat exchanger 29 , to flow out of the gas cooler 28 and Since the refrigerant flowing into the electric expansion valve 33 flows into the second flow path 29B of the heat exchanger 29 , it can pass through the low-pressure side refrigerant flowing in the first flow path 29A of the heat exchanger 29 to the second flow path of the heat exchanger 29 . The refrigerant on the high-pressure side flowing through the second flow path 29B is subcooled, so that the dryness of the refrigerant at the outlet of the electric expansion valve 33 can be reduced.

The refrigerant flowing in the second flow path 29B of the heat exchanger 29 enters the accumulator 36 through the electric expansion valve 33 , flows out from the lower part of the liquid accumulator 36 and flows into the evaporator 41 after being throttled by the electric expansion valve 39 , so Subcooling in the heat exchanger 29 reduces the dryness of the refrigerant at the outlet of the electric expansion valve 33 and increases the liquid phase ratio of the refrigerant sent to the electric expansion valve 39 , thereby effectively improving the refrigerating capacity.

In addition, part of the refrigerant liquefied by expansion in the electric expansion valve 33 evaporates in the accumulator 36 to become a gaseous refrigerant whose temperature drops, and the rest becomes liquid refrigerant and is temporarily stored in the lower part of the accumulator 36 . Then, the liquid refrigerant in the lower part of the accumulator 36 will flow into the electric expansion valve 39, so that the refrigerant can flow into the electric expansion valve 39 in a liquid-filled state, and especially the refrigerated condition with high evaporation temperature in the evaporator 41 can be realized. Under the improvement of the freezing ability. Furthermore, since the accumulator 36 absorbs fluctuations in the amount of circulating refrigerant in the refrigerant circuit 1, there is also an effect of eliminating errors in the amount of refrigerant charged.

In particular, it includes a bypass circuit 60 connected in parallel to the series circuit of the electric expansion valve 39 and the evaporator 41 , and an electric expansion valve 65 provided in the bypass circuit 60 , and the control device 57 makes the refrigerant flow through the electric expansion valve 65 . The first flow path 29A flowing into the heat exchanger 29 bypassing the electric expansion valve 39 and the evaporator 41 controls the suction temperature of the refrigerant evaporated therein and sucked into the low-pressure side of the compressor 11 to a predetermined target value. A rise in the suction temperature of the refrigerant in the compressor 11 can be prevented, and a decrease in the operating efficiency of the compressor 11 or occurrence of damage can be avoided beforehand.

In addition, the control device 57 controls the high-pressure side pressure of the refrigerant circuit 1 upstream of the electric expansion valve 33 to a predetermined target value through the electric expansion valve 33 , so that the high-pressure side pressure of the refrigerant discharged from the compressor 11 can be reduced to a predetermined target value. The operating efficiency of the compressor 11 decreases due to the increase in temperature, or the problem of damage to the compressor 11 is avoided.

In addition, the auxiliary circuit 48 has an electric expansion valve 43 and a gas pipeline 42 that allows the refrigerant to flow out from the upper part of the accumulator 36 and flow into the electric expansion valve 43. The control device 57 transfers the refrigerant in the liquid accumulator 36 to Therefore, the electric expansion valve 43 suppresses the influence of pressure fluctuations on the high pressure side, thereby controlling the pressure of the refrigerant sent from the lower part of the accumulator 36 to the electric expansion valve 39 .

In addition, the pressure of the refrigerant flowing into the electric expansion valve 39 is lowered by the electric expansion valve 43 , so that a pipe with low pressure resistance strength can be used as the refrigerant pipe 8 leading to the electric expansion valve 39 . Thereby, improvement of workability and construction cost can be aimed at. In particular, the pressure in the accumulator 36 is lowered by extracting low-temperature gas from the upper portion of the accumulator 36 through the electric expansion valve 43 . As a result, the temperature in the accumulator 36 drops, and condensation of the refrigerant occurs, whereby the refrigerant in a liquid state can be efficiently stored in the accumulator 36 .

In addition, the auxiliary circuit 48 has an electric expansion valve 47 and a liquid pipe 46 that allows the refrigerant to flow out from the lower part of the accumulator 36 and flow into the electric expansion valve 47 . Since the discharge temperature of the refrigerant of the cooler 28 is controlled to a predetermined target value, it is possible to spray the intermediate pressure portion of the compressor 11 to cool the compressor 11, and the compressor 11 and the refrigerant sprayed from the compressor 11 The problem of the output temperature becoming too high can be avoided before it happens.

Furthermore, a gas cooler blower 31 for cooling the gas cooler 28 is provided, and the controller 57 controls the operation of the gas cooler blower 31 so that the temperature of the refrigerant flowing out of the gas cooler 28 is determined relative to the temperature of the outside air. Therefore, the temperature of the refrigerant at the outlet of the gas cooler 28 can be maintained at an appropriate value while suppressing unnecessary operation of the gas cooler blower 31 for air cooling the gas cooler 28 . On the other hand, the high-pressure side pressure only needs to be controlled by the electric expansion valve 33 , and these measures can protect the compressor 11 and maintain stable operation.

In particular, when carbon dioxide is used as in the examples, it is possible to effectively improve the freezing capacity and improve the performance.

[Example 2]

Next, another embodiment of the present invention will be described with reference to FIGS. 3 and 4 . In addition, in FIG. 3 and FIG. 4 , parts marked with the same reference numerals as those in FIG. 1 and FIG. 2 are the same or have the same function. In the case of the present embodiment, an internal heat exchanger 68 is added to the refrigerant circuit 1 of FIG. 1 . This internal heat exchanger 68 is provided in the refrigerant circuit 1 on the downstream side of the accumulator 36 and on the upstream side of the electric expansion valve 39 (primary throttling mechanism).

The internal heat exchanger 68 has a first flow path 68A and a second flow path 68B, and the first flow path 68A is interposed in the refrigerant introduction pipe 22 between the connection point with the bypass circuit 60 and the first flow path 29A of the heat exchanger 29 Among them, the second flow path 68B is interposed in the accumulator outlet pipe 37 before branching off from the liquid pipe 46 . With this configuration, the first flow path 68A through which the refrigerant flowing out of the evaporator 41 and the refrigerant on the low-temperature, low-pressure side of the bypass circuit 60 flow, the flow from the accumulator 36 to the accumulator outlet pipe 37 and the The liquid refrigerant flowing through the second flow path 68B is subcooled. In addition, the refrigerant passing through the bypass circuit 60 is throttled by the electric expansion valve 65 , and evaporates in the first flow path 68A to exert a cooling effect.

The portion indicated by X3 in the P-h diagram of FIG. 4 is the effect of the internal heat exchanger 68, which can reduce the temperature of the refrigerant flowing into the electric expansion valve 39 from the state indicated by the solid line to the state indicated by the dotted line. In this way, by further providing the internal heat exchanger 68 in the refrigerant circuit 1 downstream of the accumulator 36 and upstream of the electric expansion valve 39, the refrigerant flowing out of the evaporator 41 to the heat exchanger 29 flows into the internal heat exchange The first flow path 68A of the receiver 68 allows the refrigerant that flows out from the lower part of the accumulator 36 and flows to the electric expansion valve 39 to flow into the second flow path 68B of the internal heat exchanger 68, thereby allowing the refrigerant to pass through the internal heat exchanger 68. The low-pressure side refrigerant flowing in the first flow path 68A supercools the refrigerant flowing out of the accumulator 41 and flowing in the second flow path 68B of the internal heat exchanger 68 , thereby suppressing the flow from the accumulator 36 . The reexpansion of the liquid refrigerant that flows out and flows to the electric expansion valves 39, 47, 65 realizes further improvement of the refrigeration capacity.

Claims (8)

1. Refrigeration device, the refrigerant circuit is composed of compression mechanism, gas cooler, main throttling mechanism and evaporator, and the high pressure side reaches supercritical pressure. The refrigeration device includes: A throttling mechanism for pressure adjustment connected to the refrigerant circuit on the downstream side of the gas cooler and upstream of the main throttling mechanism; a liquid receiver connected to the refrigerant circuit on the downstream side of the pressure adjustment throttling mechanism and on the upstream side of the main throttling mechanism; a heat exchanger provided in the refrigerant circuit on the downstream side of the gas cooler and on the upstream side of the pressure adjustment throttle mechanism; The main circuit is from the gas cooler to the liquid receiver through the heat exchanger and the pressure adjustment throttling mechanism, so that the refrigerant flows out from the lower part of the liquid receiver and flows into the main throttling mechanism; an auxiliary circuit for returning the refrigerant in the accumulator to the intermediate pressure part of the compression mechanism through the auxiliary throttling mechanism; a bypass circuit connected in parallel with respect to the series circuit of said main throttling mechanism and said evaporator; A throttling mechanism for bypass is arranged in the bypass circuit; and a control mechanism for controlling the pressure adjustment throttle mechanism, the auxiliary throttle mechanism, and the bypass throttle mechanism, The refrigerant flowing out of the evaporator and sucked into the compression mechanism flows into the first flow path of the heat exchanger, and the refrigerant flowing out of the gas cooler into the pressure adjustment throttle mechanism flows into the first flow path of the heat exchanger. The second flow path of the heat exchanger to subcool the refrigerant flowing in the second flow path of the heat exchanger by the refrigerant flowing in the first flow path of the heat exchanger. 2. The freezing device of claim 1, The control means controls the suction temperature of the refrigerant sucked into the low-pressure side of the compression mechanism to a predetermined target value through the bypass throttling mechanism. 3. A freezing device as claimed in claim 1 or 2, including an internal heat exchanger disposed in the refrigerant circuit on the downstream side of the accumulator and on the upstream side of the primary throttling mechanism, The refrigerant that flows out of the evaporator and flows into the heat exchanger flows into the first flow path of the internal heat exchanger, and the refrigerant that flows out of the lower part of the accumulator and flows into the main throttling mechanism flows into The second flow path of the internal heat exchanger so that the refrigerant flowing in the second flow path of the internal heat exchanger is cooled by the refrigerant flowing in the first flow path of the internal heat exchanger too cold. 4. Freezing device as claimed in claim 1 or 2, The control means controls the high-pressure side pressure of the refrigerant circuit on the upstream side of the pressure-adjusting throttle mechanism to a predetermined target value through the pressure-adjusting throttle mechanism. 5. Freezing device as claimed in claim 1 or 2, The auxiliary throttling mechanism has a throttling mechanism for a first auxiliary circuit, The auxiliary circuit has a gas pipe for letting the refrigerant flow out from the upper part of the accumulator and flow into the throttling mechanism for the first auxiliary circuit, The control means controls the pressure of the refrigerant in the accumulator to a predetermined target value through the expansion means for the first auxiliary circuit. 6. The freezing device of claim 1 or 2, The auxiliary throttling mechanism has a throttling mechanism for a second auxiliary circuit, The auxiliary circuit has a liquid pipe for letting the refrigerant flow out from the lower part of the accumulator and flow into the throttling mechanism for the second auxiliary circuit, The control means controls the discharge temperature of the refrigerant discharged from the compression mechanism to the gas cooler to a predetermined target value through the expansion mechanism for the second auxiliary circuit. 7. The freezing device of claim 1 or 2, comprising a blower for air cooling said gas cooler, The control means controls the operation of the blower so that the temperature of the refrigerant flowing out of the gas cooler becomes a predetermined target value determined based on the outside air temperature. 8. The freezing device of claim 1 or 2, Carbon dioxide is used as the refrigerant.